This is faster than using the software implementation, and the insn is available on all half-way recent hardware. Use the respective compiler builtins when available.
Signed-off-by: Jan Beulich <jbeul...@suse.com> Reviewed-by: Jason Andryuk <jandr...@gmail.com> --- a/xen/arch/x86/include/asm/bitops.h +++ b/xen/arch/x86/include/asm/bitops.h @@ -475,9 +475,16 @@ static inline int fls(unsigned int x) * * The Hamming Weight of a number is the total number of bits set in it. */ +#ifdef __POPCNT__ +#define hweight64(x) __builtin_popcountll(x) +#define hweight32(x) __builtin_popcount(x) +#define hweight16(x) __builtin_popcount((uint16_t)(x)) +#define hweight8(x) __builtin_popcount((uint8_t)(x)) +#else #define hweight64(x) generic_hweight64(x) #define hweight32(x) generic_hweight32(x) #define hweight16(x) generic_hweight16(x) #define hweight8(x) generic_hweight8(x) +#endif #endif /* _X86_BITOPS_H */
